Great attention is focused on electrical powered vehicles such as an electric vehicle and hybrid vehicle as environment-friendly vehicles. An electric vehicle has a vehicle-mounted battery charged from a power source external to the vehicle, and the motor is driven using the charged electric power for running. A hybrid vehicle refers to a vehicle incorporating an engine as a power source, in addition to a motor, or a vehicle further incorporating a fuel cell as the direct current power source for driving the vehicle.
Among the hybrid vehicles there is known a vehicle that allows charging of the vehicle-mounted battery from a power source external to the vehicle, likewise with an electric vehicle. For example, the so-called “plug-in hybrid vehicle” is known that allows the battery to be charged from a general household power supply by establishing connection between the plug socket located at an establishment and the charging inlet provided at the vehicle through a charging cable.
As a method for power transfer, attention is recently focused on wireless electrical power transmission without using power supply cords and/or cables for electrical transmission. Three promising approaches of this wireless power transfer technique are known, i.e. power transfer using electromagnetic induction, power transfer using micro waves, and power transfer through the resonance method.
The resonance method thereof is a non-contact power transfer approach transferring power via an electromagnetic field by causing resonance at a pair of self-resonant coils (near field) via the electromagnetic field, allowing electric power as high as several kW to be transferred over a relatively long distance (for example, several meters) (refer to Non-Patent Document 1).    Patent Document 1: Japanese Patent Laying-Open No. 8-237890    Non-Patent Document 1: Andre Kurs et al., “Wireless Power Transfer via Strongly Coupled Magnetic Resonances”, [online], Jul. 6, 2007, Science, Volume 317, p. 83-86, [Searched on Sep. 12, 2007], Internet <URL; http://www.sciencemag.org/cgi/reprint/317/5834/83.pdf>